igneous

Scoria (Lava Rock)

Scoria (extrusive volcanic rock)

Hardness: 5-6 Mohs scale; Color: Dark red, black, or dark brown; Luster: Dull/Earthy; Crystal Structure: Amorphous/Vesicular; Cleavage: None; Specific Gravity: Low (often floats briefly on water)

Hardness: 5-6 Mohs scale
Color: Dark red, black, or dark brown
Luster: Dull/Earthy

Identified April 1, 2026More igneous →

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Physical properties

Hardness: 5-6 Mohs scale; Color: Dark red, black, or dark brown; Luster: Dull/Earthy; Crystal Structure: Amorphous/Vesicular; Cleavage: None; Specific Gravity: Low (often floats briefly on water)

Formation & geological history

Formed from gas-rich basaltic or andesitic magma. As the magma erupts and cools rapidly at the surface, trapped gas bubbles form small, rounded cavities called vesicles.

Uses & applications

Used in landscaping, gas grills (lava rocks), drainage systems, high-temperature insulation, and as a lightweight aggregate in concrete.

Geological facts

Scoria differs from pumice because it has larger vesicles and thicker cell walls, making it dense enough to usually sink in water, whereas pumice often floats. It is a major component of cinder cones.

Field identification & locations

Identify by its highly vesicular (bubbly) texture, lightweight feel, and rough, abrasive surface. Commonly found near active or dormant volcanic cinder cones in places like Hawaii, Iceland, and the American Southwest.

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Blue Apatite

Fluorapatite (Ca5(PO4)3F)

mineral

Dark Igneous Rock (Likely Basalt or Diabase)

Basalt (extrusive igneous rock) or Diabase (intrusive igneous rock - also known as Dolerite), largely composed of plagioclase feldspar, pyroxene (augite), and sometimes olivine and amphibole. Exact mineralogy would require thin section analysis.

Igneous